How to control a goiter?

Depends on cause. If it is a diffuse goiter, it may be caused by high tsh, which can arise in hypothyroidism or iodine deficiency (rare in usa, as salt is iodinated) or excessive goitrogens in susceptible ppl (like cauliflower). Treating the hypothyroidism can slow growth, if the above is the cause. If enlarging modules is the cause, surgery. Depends on cause, radioactive iodine may help.
Depends on type. A goiter, or enlarged thyroid gland, may result from: hypothyroidism, iodine (i) deficiency, thyroid nodules, or graves' disease. Thyroid hormone and i replacement can control goiter associated with hypothyroidism and i deficiency respectively. Radioactive i-131 treatment can shrink the goiter and lower thyroid function in nodular disease or graves', although some patients need surgery to do this.